Products made from a fibrous web are used for a variety of purposes. For example, paper towels, facial tissues, toilet tissues, napkins, and the like are in constant use in modern industrialized societies. The large demand for such paper products has created a demand for improved versions of the products. If the paper products such as paper towels, facial tissues, napkins, toilet tissues, mop heads, and the like are to perform their intended tasks and to find wide acceptance, they must possess certain physical characteristics.
Among the more important of these characteristics are strength, softness, absorbency, and cleaning ability. Strength is the ability of a paper web to retain its physical integrity during use. Softness is the pleasing tactile sensation consumers perceive when they use the paper for its intended purposes. Absorbency is the characteristic of the paper that allows the paper to take up and retain fluids, particularly water and aqueous solutions and suspensions. Important not only is the absolute quantity of fluid a given amount of paper will hold, but also the rate at which the paper will absorb the fluid. Cleaning ability refers to a fibrous structures' capacity to remove and/or retain soil, dirt, or body fluids from a surface, such as a kitchen counter, or body part, such as the face or hands of a user.
Through-air drying papermaking belts comprising a reinforcing element and a resinous framework, and/or fibrous webs made using these belts are known and described, for example, in the following commonly assigned U.S. Pat. No. 4,528,239, issued Jul. 9, 1985 to Trokhan. Trokhan teaches a belt in which the resinous framework is joined to the fluid-permeable reinforcing element (such as, for example, a woven structure, or a felt). The resinous framework may be continuous, semi-continuous, comprise a plurality of discrete protuberances, or any combination thereof. The resinous framework extends outwardly from the reinforcing element to form a web-side of the belt (i. e., the surface upon which the web is disposed during a papermaking process), a backside opposite to the web-side, and deflection conduits extending therebetween. The deflection conduits provide spaces into which papermaking fibers deflect under application of a pressure differential during a papermaking process. Because of this quality, such papermaking belts are also known in the art as “deflection members.” The terms “papermaking belt” and “deflection member” may be used herein interchangeably.
Papers produced on deflection members disclosed in Trokhan are generally characterized by having at least two physically distinct regions: a region having a first elevation and typically having a relatively high density, and a region extending from the first region to a second elevation and typically having a relatively low density. The first region is typically formed from the fibers that have not been deflected into the deflection conduits, and the second region is typically formed from the fibers deflected into the deflection conduits of the deflection member. The papers made using the belts having a continuous resinous framework and a plurality of discrete deflection conduits dispersed therethrough comprise a continuous high-density network region and a plurality of discrete low-density pillows (or domes), dispersed throughout, separated by, and extending from the network region. The continuous high-density network region is designed primarily to provide strength, while the plurality of the low-density pillows is designed primarily to provide softness and absorbency. Such belts have been used to produce commercially successful products, such as, for example, BOUNTY® paper towels, and CHARMIN® toilet tissue, all produced and sold by the instant assignee.
Typically, certain aspects of absorbency of a fibrous structure are highly dependent on its surface area. That is, for a given fibrous web (including a fiber composition, basis weight, etc.), the greater the web's surface area the higher the web's absorbency and, for certain structured webs, cleaning ability. In the structured webs, the low-density pillows, dispersed throughout the web, increase the web's surface area, thereby increasing the web's absorbency. The three-dimensionality of the structured web can improve the web's cleaning ability by providing increased scrubbing surfaces. However, increasing the web's surface area by increasing the area comprising the relatively low-density pillows would result in decreasing the web's area comprising the relatively high-density network area that imparts the strength. That is, increasing a ratio of the area comprising pillows relative to the area comprising the network would negatively affect the strength of the paper, because the pillows have a relatively low intrinsic strength compared to the network regions. Therefore, it would be highly desirable to minimize the trade-off between the surface area of the high-density network region primarily providing strength, and the surface area of the low-density region primarily providing softness and absorbency.
An improvement on deflection members to be used as papermaking belts to provide paper having increased surface area is disclosed in commonly assigned U.S. Pat. No. 6,660,129, issued Dec. 9, 2003 to Cabell et al. The disclosure of Cabell et al. teaches a deflection member that increases surface area by creating a fibrous structure wherein the second region comprises fibrous domes and fibrous cantilever portions laterally extending from the domes. The fibrous cantilever portions increase the surface area of the second region and form, in some embodiments, pockets comprising substantially void spaces between the fibrous cantilever portions and the first region. These pockets are capable of receiving additional amounts of liquid and thus further increase absorbency of the fibrous structure.
Further, Cabell et al. teaches processes for making such deflection members via a modification of the process taught by Trokhan. In one aspect, the deflection member comprises a multi-layer framework formed by at least two UV-cured layers joined together in a face-to-face relationship, and the framework is joined to a reinforcing element. Each of the layers has a deflection conduit portion. The deflection conduit portion of one layer is fluid-permeable and positioned such that portions of that layer correspond to the deflection conduits of the other layer and thus comprise a plurality of suspended portions. Cabell et al. teaches making the deflection member by curing a coating of a curable material through a mask comprising opaque regions and transparent regions and a three-dimensional topography.
However, the deflection member and process of Cabell et al. has the drawback of being unable to achieve uniform patterns of cantilevered portions. That is, the shape, size and distribution of discrete protuberances having cantilevered portions is randomly determined. This is because the use of a mask and UV-curable resins imposes certain inherent limitations on the topography of the framework that can be joined to a reinforcing member, including the shape, size and distribution of discrete protuberances. Specifically, the topography of the framework of the deflection member is dictated by the mask (or masks, in a two-layer version), and therefore the choice of topographies for the deflection member is limited to those for which a suitable mask can be produced.
Efforts at improving masks to provide broader choices in UV-curing and joining the framework to the reinforcing member are ongoing, and include, for example, the technological approach described in U.S. Provisional Application 62/076,036, entitled Mask and Papermaking Belt Made Therefrom, filed by Seger et al. on Nov. 6, 2014. Seger et al. teaches a three-dimensional mask that permits certain improvements in mask design to permit greater design freedom for non-random, discrete protuberances for making paper structures having increased surface area. The surface area is produced in deflection conduits that are non-randomly achieved, that is, the mask is designed such that a pattern of non-random shapes, sizes, and distribution of protuberances on the deflection member can be achieved.
However, the deflection member of Seger et al. is not designed to produce fibrous structures described in Cabell et al. as cantilevered portions. That is, while Seger et al. can produce novel structures for protuberances that are non-random with respect to shape, size, and distribution, the novel structures do not appear to produce cantilevered structures useful for increasing absorbency and cleaning ability of fibrous structures made thereon.
Accordingly, there is an unmet need for a deflection member having a three-dimensional topography unachievable by technology that relies on UV-curing a framework to be joined to a reinforcing member.
Further, there is an unmet need for fibrous structures such as sanitary tissue paper products having a three-dimensional structure unachievable with current deflection conduits having a topography made by technology that relies on UV-curing a framework to be joined to a reinforcing member.
Additionally, there is an unmet need for a method for making a deflection member having a three-dimensional topography unachievable by technology that relies on UV-curing a framework to be joined to a reinforcing member.
Additionally, there is an unmet need for a unitary deflection member having a similar structure to those made by UV-curing a framework to be joined to a reinforcing member.
Additionally, there is an unmet need for a deflection member having a pattern of regularly oriented and sized deflection members having protuberances with cantilevered structures.
Additionally, there is an unmet need for a deflection member having protuberances with cantilevered structures, the protuberances of each being made according to a predetermined design with respect to shape, size and distribution.